Magneto-electric machine



. Nov. 3, 1936. c s 2,059,745

' MAGNETO-ELECTRIC MACHINE I Filed Oct. 19, 1934 IN VEN TOR.

I C'uRr F PIE/6 BY fi q Zeno ATTORNEY.

Patented Nov. 3, 1936 PATENT OFFICE MAGNETO -ELECTRIC MACHINE Curt F. Reis, Beloit, Wis., assignor to Fairbanks, Morse & Company, Chicago, 111., a corporation of Illinois Application October 19, 1934, Serial No. 748,996

8 Claims.

This invention relates to improvements in magneto electric machines, and more particularly to improvements in rotors of magnetos of the rotating field type employing an assembly of permanent magnets, as well as improvements in methods of forming such assemblies.

In certain prevailing types of magneto rotors it is usual to employ a mass of cast non-magnetic metal, such for example as an alloy of aluminum or zinc, for positioning the magnet bars in assembly to the rotor shaft. It is well known that in the process of die-casting, the cast metal will inevitably absorb a substantial quantity of iron particles from the metallic dies or molds. As a result of such absorption of iron particles by the cast rotor body, a magnetic bridge or path is or may be formed between the several permanent magnet bars, and thus permit magnetic leakage losses to occur through the cast body. It is Well known that aluminum alloys possess a high affinity for iron, and particularly so when subjected to the high temperatures and pressures of the die-casting process. Accordingly, an object of the present invention is to provide an improved rotor for magnetos of the type noted, which includes a mass of drop-forged non-magnetic metal such as brass, or other equivalent material, which is characterized by a low or negligible affinity for ferrous metals, for securing the permanent magnets and a magnetic bridging member to the rotor shaft. It has beenfound in practice, that a body of brass or other similar material which has been drop-forged into embracing relation with the shaft and pole pieces, provides a rotor structure of greater strength and rigidity than is attained by casting or die-casting.

Yet another object is attained in the provision of an improved and greatly simplified magneto rotor construction for magnetos of the type noted, which includes a rotor shaft formed of steel or other similar material, and a body mass of forged non-magnetic metal for securely assembling the magnet bars and a magnetic bridging member to the shaft. By this provision, a. shaft of substantial strength and rigidity is employed in the rotor assembly, and the resulting structure consists, in eifect, of a single rigid unit.

A still further object is to provide an improved rotor for magnetos which is rigid and durable in construction, is composed of forged material of substantial strength, and which results in a substantial reduction of production through minimization of material, and a subcosts,

stantial reduction in the total weight of the assembled rotor structure.

An additional object is attained in an improved rotor construction which comprises a shaft, a magnetic end plate secured to the shaft, spaced permanent magnet bars arranged parallel to the shaft and magnetically bridged on one end by the end plate, a rotor body formed of non-magnetic material and, by preference, drop-forged into embracing relation with the shaft, magnet bars and end plate, and pole shoe elements in bridging relation with certain of th magnet bars.

Further objects and advantages .will appear from the following description and from the drawing, in which:

Fig. 1 is a longitudinal sectional elevation of a preferred form of rotor structure embodying the improvements of the present invention; Fig. 2 is an end elevation of the preferred rotor, as viewed from line 22 of Fig. 1, and Figs. 3, 4 and are transverse sections taken along lines 3-3, 4--4, and 5-5, respectively, of Fig. 1.

It will be understood that the improvements of the present invention are confined only to the rotor structure of a magneto electric machine of the rotating field type, or the like. The secondary or stator structure of the machine, which forms no part of the present invention, may be arranged according to usual practice, or in any other manner suitable to an operative organizaion.

Referring now to the drawing by characters of reference, the numeral [0 designates, generally, a presently preferred form of rotor structure embodying the improvements of the present invention. The rotor structure comprises a shaft ll formed of steel or other suitable material having the required strength, together with spaced magnet bars or pole pieces l2 arranged parallel to the shaft H and to each other. In the presently preferred example, the pole pieces 12 are formed of cobalt steel, as this steel is characterized by a high magnetic retentivlty, a feature which is highly desirable in rotor bars for magneto rotor constructions of the type noted. However, any other highly coercive magnetic material may be employed in forming the pole pieces, as desired. The pole pieces are formed, by preference, of a circular cross-section to facilitate such machining operations as are necessary. In the present example shown, the rotor includes four magnet bars or poles, al-

may be varied according to the type and requirethough it will be understood that the number,

ments of the magneto in which the rotor is to be utilized.

A magnetic bridging member or plate l3 of stamped soft iron or steel, is disposed transversely of the shaft near one end of the rotor, and in contact with end faces ll of the pole pieces. This bridging member provides a flux path common to all the pole pieces. Keyways may be provided in the shaft toreceive and seat a shaft key element, such as l5, for preventing any relative rotational movement of the shaft and other parts of the rotor.

The improved method of forming the rotor consists in suitably positioning the pole pieces I2, the bridging member l3 together with the rotor shaft II, in the spaced relation of their final assembly. Suitable clamping studs (not shown) are displaceably provided, prior to forging, opposite the ends of and aligned with each pole piece l2, and at one end of the rotor adjacent the magnetic bridging member l3, the studs corresponding in size and shape with, and so as to result in channels l5. Suitable means (not shown) are provided for applying pressure inwardly upon the clamping studs between the magnetic bridging member i3 and the opposite ends of the pole pieces l2, so as to maintain the ends of the pole pieces in contact with the bridging member, prior to and during the dropforging process. A mass of non-magnetic metal ll, such as brass or other similar metal possessing a negligible affinity for iron or other metals or alloys of the ferrous group, isthen drop-forged about the assembled elements for intimately uniting in assembly to the shaft II, the pole pieces l2 and bridging member l3. Following this, laminated pole shoes I8, the laminations of which are each provided with an aperture l9,

are assembled on the free ends of the pole pieces, the pole pieces thus extending through the laminations stacked thereover. The laminations are, by preference, secured in place on the pole pieces, following their compression, by means of split rings 20 or the equivalent, which are formed of resilient material and disposed in grooves 2| provided peripherally of, and near the free end of each of the pole pieces. These rings, when snapped into the positions shown, serve securely to fasten the laminated pole shoes in place. The rotor is now completely assembled and ready for use.

The body I1 is, by preference, formed of a suitable non-magnetic material having a negligible affinity for iron or other metals or alloys of the ferrous group. Brass has been found to provide suitable material for this purpose, and one which is presently preferred, since that metal possesses a high tensile strength and a low affinity for ferrous metals. The mass of metal forming the body I! may be either dropforged or die-cast into assembled relation with the pole pieces, bridging member and shaft, to result, upon application of the laminated shoes, in the rotor illustrated. The drop-forging method is, however, preferred in the present example. My further preference is to heat the metal to be forged, although the metallic mass is not required to be heated to any higher degree than is necessary to provide a softened or plastic state of the metal.

For reasons of economy in metal and to minimize the weight of the rotor structure, it is my preference to form the mass ll of an axial length substantially less than that of the bars or pole pieces I2, and further, to form the body over a greater portion of its axial length with a reduced cross-sectional area, the preferred sectional configuration being that of a cross, or substantially X shape, as illustrated by Fig. 4. The portion of the body I! in engagement with the plate II is, by preference, formed as a cylindrical section 22 (Figs. 1 and 3), for effecting a substantial enclosure of the plate element. The remainder of the body is, by preference, formed of the reduced sectional area, and in effect comprises a hub portion 23 engaging the shaft II, and

spaced, parallel cylindrical portions 24 in engagement with the pole pieces I 2 and suitable channels 25 between adjacent pole pieces. By this arrangement, only a minimum amount of metal consistent with the strength requirements for a rotor structure 01' the type described, need be employed in forming the assembly. Moreover, a substantial reduction in the weight of the completed rotor assembly will be effected and the tendency for magnetic leakage losses substantially reduced.

The rotor shaft and pole pieces are, by preference, provided with grooved portions 26 and 21 to insure good interlocking securement between the mass of forged metal, and the shaft and pole pieces. These portions, due to an improved bond, prevent relative movement between the body mass, the shaft and the pole pieces, either angularly or longitudinally of the shaft and magnet bars.

By reducing the mass and dimensions of the body of metal ll, according to the practices herein disclosed, a material reduction in the volume and weight of non-magnetic materials is effected, as is the cost of the finished rotor, in comparison with rotors of existing constructions.

An additional advantage in the present arrangement of parts, may be found in the substantial length of free end portion of the magnet bars, which facilitates re-magnetization of the bars.

It is to be understood that the presently preferred embodiment of the invention in no way limits the invention, as substantial alterations or modifications may be made thereto, without departing from the spirit and full intended scope of the invention, as defined by the appended claims.

I claim:

1. In a rotor structure for magnetos of the rotating field type, a shaft, pole pieces arranged parallel to the shaft, the shaft and pole pieces being circumferentially grooved, a magnetic bridging element engaging corresponding end faces of certain of said pole pieces, a one-piece body formed of a non-magnetic metal characterized by a relatively low aflinity for ferrous materials, the body including a substantially cylindrical base portion, and tubular portions projected in an axial direction therefrom, the metal of the body being in permanently-compressed embracing relation to the grooved portions of said shaft and pole pieces and about the bridging element, said body being of an axial length substantially less than that of the pole pieces, so that end portions of the pole pieces project beyond the body, pole shoes on the projecting ends of certain of the pole pieces, with the inner faces of the shoes abutting said tubular portions, and means externally engaging the extremities of the pole pieces, in positions to secure said shoes in assembly on the pole pieces in abutting relation with said tubular portions.

2. In a rotor structure for magnetos of the rotating field type, a shaft, pole pieces arranged parallel to each other and to the shaft, a magnetic bridging element engaging corresponding end faces of certain of the pole pieces, and a unitary body of a non-magnetic metal having a low aflinity for ferrous materials, said body including a substantially enlarged section containing end portions of the pole pieces and the bridging element, and a plurality of parallel cylindrical portions on said section, there being one such cylindrical portion for each pole piece, together with bridges between the cylindrical portions providing a shaft receiving portion, the metal of the body being in permanently-compressed embracing relation with said bridging element, shaft and pole pieces, and serving to maintain a magnetic contact between said pole pieces and bridging element.

3. In a rotor structure for magnetos of the rotating field type, a shaft, pole pieces arranged parallel to the shaft, a magnetic bridging element engaging corresponding end faces of said pole pieces, and a unitary body of a non-magnetic material characterized by a low affinity for ferrous materials, the metal of the body being in permanently compressed embracing relation with said shaft, pole pieces and bridging element, said body including a hub portion about said shaft, peripherally spaced, longitudinally extending cylindrical portions embracing said pole pieces, and an enlarged portion near one end of the body, embracing said bridging element, the compressed condition of said enlarged portion serving to maintain the pole pieces and bridging element in intimate magnetic contact.

4. In a rotor structure for magnetos of the rotating field type, a shaft circumferentially grooved over a portion thereof, pole pieces arranged parallel to each other and to the shaft, each of the pole pieces being grooved about one end portion thereof, a magnetic element bridging certain of the pole pieces, a one-piece body formed of a non-magnetic metal characterized by a relatively low affinity for ferrous material the body metal being in permanently-compressed embracing relation with said shaft, pole pieces and bridging element, and occupying the grooved portions of the shaft and pole pieces, for effecting a permanent assembly of the rotor parts and the body, the body extending only over a portion of the length of the pole pieces, leaving a free end of each pole piece projecting beyond the body, the body being of substantially cross-shape in transverse section where it engages the polepieces, and characterized by a substantially cylindrical base portion enclosing the bridging element and maintaining same compressed against the pole pieces, pole shoe assemblies on the free ends of ,certain of the pole pieces, and abutting end portions of the body, and means externally engaging the free ends of the pole pieces, for securing the pole shoe assemblies thereon.

5. The herein described method of forming an assembly of permanent magnets, which consists in positioning the magnets in their final relation, and while so positioned, drop-forging a body of metal in holding relation to the magnets.

6. The herein described method of forming an assembly of permanent magnets, which consists in positioning the magnets in their final relation, so arranging other elements of magnetic material as to bring the magnets into the desired circuit relation, and in drop-forging a body or frame of metal into holding relation to the magnets, and in such relation as to secure certain of said other elements in intimate contact with the magnets.

7. The herein described method of forming a rotor for a magneto of the rotating field type, which consists in positioning pole pieces, elements to be magnetically associated therewith, and a. shaft, in the relation of their final assembly, in forging a body of metal about the elements and shaft, and about a part only of the several pole pieces to secure the elements and pole pieces in assembly with the shaft, in stacking laminations over the remaining portions of the pole pieces to form pole shoes, and in clamping the pole shoes on the pole pieces.

8. The herein described method of forming a rotor for a magneto of the rotating-field type, which consists in notching a plurality of bar magnets, notching a rotor shaft, positioning the shaft and magnets in spaced parallel relation with a bridging plate adjacent the magnets, in forging a body of non-magnetic metal, while in a plastic state, about the notched portions of the shaft and magnets and in embracing relation to the bridging plate to secure them into assembly, leaving projecting portions of the magnets, in stacking pole shoe elements upon the projecting magnet portions, and in yieldably clamping the shoe elements to the magnets.

CURT F. REIS. 

